Liquid crystal display and method of fabricating the same

ABSTRACT

An MVA liquid crystal display which is high in brightness and has preferable characteristics is provided. Further, the MVA liquid crystal display with a preferable display quality as well as a larger margin in fabrication and a higher yield is provided. A first substrate having a first electrode, a second substrate having a second electrode corresponding to a display pixel, the liquid crystal having negative dielectric anisotropy sealed between the first and the second substrates, and a structure which is provided on each of the first and the second substrate to control an alignment of the liquid crystal are provided. The structure in the first substrate has a linear protrusion structure and provides at least two auxiliary protrusion structures opposing to each end portion facing to the second electrode extending from a protrusion structure provided and the width between the two auxiliary protrusions and the opposing second electrode is more than 6 μm respectively.

This is a divisional of application Ser. No. 10/726,117, filed Dec. 2,2003, which is a divisional of application Ser. No. 09/611,846, filedJul. 7, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display for atelevision, display and the like and its fabrication method.Specifically, the present invention relates to a liquid crystal displaycontaining a vertical alignment liquid crystal with large viewing angleand its fabrication method.

2. Description of the Related Art

The liquid crystal display contains the liquid crystal inserted betweena pair of substrates. Each of the pair of substrates has an electrodeand an alignment film. A TN (Twisted Nematic) mode liquid crystaldisplay widely used in the past contains the liquid crystal having ahorizontal alignment film and positive dielectric anisotropy, and whenno voltage is applied, the liquid crystal is aligned substantiallyparallel to the horizontal alignment film. When voltage is applied, theliquid crystal arises in the direction substantially perpendicular tothe horizontal alignment film.

Although the TN mode liquid crystal display has advantages such as acapability of miniaturization, the TN mode liquid crystal display hasdisadvantages that, first, the viewing angle is narrow and, second,contrast is low. As a method to improve the first disadvantage and toobtain the larger viewing angle, there is an alignment division.According to the alignment division, a single pixel is divided into twoareas and the liquid crystal is made to arise and lie down to onedirection in one area while the liquid crystal is made to arise and liedown to the other direction in the other area, thereby forming the areaswith different viewing angle characteristics within a single pixel. Whenobserved as a whole, the viewing angle characteristics are leveled and alarger viewing angle is obtained.

In order to control the alignment of the liquid crystal, rubbing isusually performed on the alignment film. When domain dividing isperformed, one area of the single pixel is rubbed in a first directionby using a mask and the other area of the single pixel is rubbed in asecond direction which is the opposite direction from the firstdirection by using a complementary mask. As another way, the wholealignment film may be rubbed in the first direction and ultravioletirradiation is selectively performed in one area or in the other area ofthe single pixel by using the mask, thereby creating a difference inpre-tilt in the liquid crystal between in one area and the other area.

Since the liquid crystal display using the horizontal alignment filmrequires rubbing, damages generated by contamination or staticelectricity occurring during the rubbing process is a main cause ofreduction in yield.

On the other hand, in a VA (vertically Aligned) mode liquid crystaldisplay using the vertical alignment film, when no voltage is applied,the liquid crystal is aligned substantially perpendicular to thevertical alignment film and when voltage is applied, the liquid crystallies down in the horizontal direction to the vertical alignment film. Inthis way, high contrast is obtained and the low contrast, which is thesecond disadvantage of the TN mode liquid crystal display above, iseliminated. However, rubbing is also normally performed on the alignmentfilm to control the alignment of the liquid crystal in the general VAmode liquid crystal display using the vertical alignment film.

The Japanese Patent Application No. 10-185836 by the applicant of thisapplication proposes a liquid crystal display which can control thealignment of the liquid crystal without rubbing. This liquid crystaldisplay is a VA mode liquid crystal display having the verticalalignment film and the liquid crystal with negative dielectricanisotropy and has a linear structure (a protrusion or a slit) arrangedon each of the pair of substrates in order to control the alignment ofthe liquid crystal.

It will be noted, hereinafter, the VA mode liquid crystal displayaccording to this method is referred to as an MVA (Multi-domain verticalAlignment) liquid crystal display in this application.

This MVA liquid crystal display has an advantage that rubbing is notrequired and, further, the domain dividing is achieved by thearrangement of the linear structure. Therefore, this MVA liquid crystaldisplay can obtain a wide viewing angle and high contrast. Since rubbingis not required, a fabrication of the liquid crystal display is simple,the contamination to the alignment film during the rubbing process iseliminated, and reliability of the liquid crystal display is improved.

FIG. 32 is a diagram of a basic structure of the MVA liquid crystaldisplay, showing a single pixel and its periphery. Further, throughoutthe diagram, items assigned the same reference numeral indicate the samething and their repeated description is omitted.

An MVA liquid crystal display 130 is an active matrix type liquidcrystal display having a thin film transistor (hereinafter, referred toas a TFT) 14 at each pixel as a switching device, and there are a redpixel R, a green pixel G and a blue pixel B in the pixel to perform thecolor display.

On a TFT substrate where the TFT 14 is provided, a gate bus line 10partially serving also as a gate electrode of the TFT 14 and a drain busline 12 are formed. The TFT 14 consists of a drain electrode 12Dextending from the drain bus line 12, a source electrode 12S positionedfacing the drain electrode 12D, and an overlapping portion between thedrain electrode 12D and the source electrode 12S of the gate bus line10. Further, although not shown, a channel layer made of, for example,amorphous silicon (a-Si) is formed on the gate bus line. Furthermore, apixel electrode 16 connected to the source electrode 12S is formed onthe TFT substrate. In the pixel electrode 16, a slit 18 is provideddiagonally to the pixel and this slit 18 becomes a structure to controlthe alignment of the liquid crystal on the substrate side. A connectingportion 16 a is provided at the pixel electrode 16 so that the pixelelectrode 16 is not electrically separated by the slit 18. In this way,a pixel electrode 16 in a pixel is electrically connected.

Although not shown, on a color filter substrate (hereinafter, referredto as a CF substrate) where a color filter is formed, a protrusion 20 tocontrol the alignment of the liquid crystal on the CF substrate side isformed and controls the alignment of the liquid crystal together withthe slit 18 on the TFT substrate.

For example, when a diagonal distance of an XGA LCD (liquid crystaldisplay) panel is equal to 15 inches, the size of a single pixel isequal to 99 μm×297 μm, the widths of the slit 18 and the protrusion 20are equal to 10 μm each, the distance between the slit 18 and theprotrusion 20 is 25 μm. Further, the width of the connecting portion 16a of the pixel electrode 16 is equal to 4 μm and the distance between anend portion of the drain bus line 12 and an end portion of the pixelelectrode 16 is equal to 7 μm.

FIGS. 33 a, 33 b and 33 c are simplified cross sectional views at a lineI-I in FIG. 32 and shows actions of the slit 18 and the protrusion 20which are the structures to control the alignment of the liquid crystal.

FIG. 33 a shows a state of the liquid crystal when no voltage is appliedbetween the electrodes on a pair of substrates. The pixel electrode 16is formed on a glass electrode 24 on the TFT substrate side, and theslit 18 is formed on the pixel electrode 16. Further, an alignment film(vertical alignment film) 32 is formed covering the pixel electrode 16and the slit 18. On the other hand, a common electrode 26 is formed on awhole surface of a glass substrate 22, facing the pixel electrode 16,and the protrusion 20 made of an insulator (a dielectric) such asphotoresist is formed on the common electrode 26. Further, an alignmentfilm (vertical alignment film) 28 is formed covering the commonelectrode 26 and the protrusion 20.

Furthermore, a liquid crystal layer LC is in between the TFT substrateand the CF substrate, and liquid crystal molecules (indicated byellipses in the diagram) are aligned perpendicular to the alignmentfilms 32 and 28. Therefore, the liquid crystal molecules are alsoaligned perpendicular to the alignment film 28 formed on the surface ofthe protrusion 20, and the liquid crystal molecules adjacent to thesurface of the protrusion 20 are in an inclined state against the glasssubstrate 22. However, when closely observed, the liquid crystalmolecules adjacent to the surface of the protrusion 20 are not alignedperpendicular to the alignment film 28, because the liquid crystalmolecules are aligned substantially perpendicular to the glass substrate22 by the alignment film 28 in an area where the protrusion 20 is notformed and due to the continuum characteristics of the liquid crystal,the liquid crystal molecules follow the liquid crystal moleculesoccupying a portion of the pixel and are in a state inclined from thedirection perpendicular to the alignment film 28 to the direction of anormal line of the glass substrate. Also, although not shown, a pair ofpolarizing plates are arranged on the outside of the glass substrates 22and 24 in the state of cross-Nicol. Therefore, in a state where novoltage is applied, the display becomes a black display.

FIG. 33 b shows equipotential lines when voltage is applied between theelectrodes on a pair of substrates and FIG. 33 c shows the state of theliquid crystal in the case above. As shown by equipotential lines shownby dotted lines in FIG. 33 b, when voltage is applied between theelectrodes 16 and 26, distribution of an electric field in the portionwhere the slit 18 and the protrusion 20 are formed becomes differentfrom the other portion. This is because in the portion where the slit 18is formed, an oblique electric field is formed from the end portion ofthe electrode toward the opposing electrode, and in the portion wherethe protrusion 20 is formed, the electric field is distorted, since theprotrusion 20 is a dielectric provided on the electrode 26. Therefore,as shown in FIG. 33 c, the liquid crystal molecules lie toward thedirection of the arrow in the diagram. In other words, the liquidmolecules lie toward the direction perpendicular to the direction of theelectric field depending on the magnitude of the voltage, therebyproviding a white display in a state when voltage is applied. At thistime, when the protrusion 20 is arranged linearly as shown in FIG. 32,the liquid crystal molecules adjacent to the protrusion 20, having theprotrusion 20 as the boundary, lie to two substantially perpendiculardirections to the direction where the protrusion 20 is arranged. Sincethe liquid crystal molecules adjacent to the protrusion 20 are slightlyinclined toward the perpendicular direction to the substrate even whenno voltage is applied, the liquid crystal molecules adjacent to theprotrusion 20 quickly respond to the electric field and lie down,followed by surrounding liquid crystal molecules which also lie downquickly and are influenced by the electric field. In a similar manner,when the slit 18 is provided linearly as shown in FIG. 32, the liquidcrystal molecules adjacent the slit 18, having the slit 18 as aboundary, also lie to two substantially perpendicular directions to thedirection where the slit 18 is arranged.

Thus, in the area between the two alternate long and short dash lines inFIG. 33 a, the liquid crystal molecules fall down to the same direction.In other words, the area aligned in the same direction is formed. Thisarea is indicated by [A] in FIG. 32. As shown representatively by [A]through [D] in FIG. 32, since areas aligned to four different directionsare formed in a single pixel, in the MVA liquid crystal display 130,characteristics of wide viewing angle can be obtained. It will be notedthat alignment control can not only be performed when the slit 18 andthe protrusion 20 are combined as shown in FIGS. 32, 33 a, 33 b and 33c, but also when a protrusion and a protrusion or a slit and a slit, asa structure to control the alignment, are combined.

However, although wide viewing angle can be obtained in the MVA liquidcrystal display 130, an area of liquid crystal molecules that are notstable exists, and therefore, the problem of reduction in brightnessexists. In other words, when voltage is applied between the electrodes,an alignment defect area 40 shown by hatching in FIG. 32 occurs. Sincethis alignment defect area 40 is an area where the transmissivity of thelight is poor, the alignment defect area results in a reduction inbrightness when the white display is performed. When viewed in the planeof FIG. 32, this alignment defect area 40 occurs on the side where thestructures (protrusion of slit) provided on the CF substrate form anobtuse angle with an edge portion of the pixel electrode 16. Thisoccurrence of the alignment defect area 40 is caused by a lateralelectric field and the like generated by an influence of the drain busline 12 at the edge portion of the pixel electrode 16. In the area wherethis alignment defect area 40 occurs, the liquid crystal molecules liein the different alignment direction from the alignment directioncontrolled by the structures (the slit 18 and the protrusion 20 in FIG.32) provided on a pair of substrates. In other words, the alignment ofthe liquid crystal molecules is disturbed in this area due to theoccurrence of the lateral electric field and the like, thereby resultingin a deterioration in display characteristic of the MVA liquid crystaldisplay 130.

In order to solve a problem (occurrence of an alignment defect area)characteristic to this MVA liquid crystal display, the applicant of thisapplication proposes a new structure to reduce influences from a lateralelectric field and the like.

FIG. 34 shows an MVA liquid crystal display 140 according to theproposal. A distinctive feature of this structure is that an auxiliaryprotrusion 20 c extending from the protrusion 20 provided in the CFsubstrate side along an end portion of the pixel electrode 16 where thealignment defect area 40 occurs is provided. The auxiliary protrusion 20c can certainly be formed by the same material and the same process asthe protrusion 20 or can be formed separately.

FIGS. 35 a and 35 b are diagrams describing the auxiliary protrusion 20c to be formed on the CF substrate. As a structure of the CF substrate,as shown in FIG. 35 a, a method to form a black matrix BM to be formedon the CF substrate by overlaying color resins forming a color filter isproposed. This method is achieved by forming red resin R, green resin Gand blue resin B on the glass substrate 22, and overlapping, as blueresin B with green resin G, blue resin B with red resin R, and red resinR with green resin G, at each end portion. The overlapped portion is theblack matrix BM. Then, the common electrode 26 and the like are formedabove.

In the case of the CF substrate formed by such a method (hereinafter,referred to as a resin overlaying BM method), a level difference equalto approximately 0.2-1.5 μm occurs at portions indicated by circles inFIG. 35 a, in other words, at the portions color resins are overlapped.If there is the level difference like this, an electric line of forceconcentrates at the portions, thereby causing alignment defects ofliquid crystal molecules.

FIG. 35 b shows a state when the auxiliary protrusion 20 c is formed atthe portion of the level difference of the black matrix. The auxiliaryprotrusion 20 c is formed to cover the portion where there is the leveldifference. In such a state, the height d1 of the level difference isequal to approximately 0.2-1.5 μm as described above, and the heightfrom the peak portion of the auxiliary protrusion 20 c is equal toapproximately 1.0-2.0 μm. The auxiliary protrusion 20 c functions torotatably align the liquid crystal molecules by easing the inclinationat the portion where there is the level difference and not toconcentrate the electric line of force by forming a material with lowdielectric constant at the portion where there is the level differenceat an angular portion. For example, a relative dielectric constant ∈ ofthe liquid crystal is approximately 6-8 and the relative dielectricconstant ∈ of the protrusion material is approximately 3-4.

However, in the portions designated by the circles in FIG. 35 b, thereis a case when the auxiliary protrusion 20 c does not sufficiently coverangular portion due to irregularities of level difference,irregularities of locations forming the protrusion, irregularities ofthe protrusion shape and the like.

FIGS. 36 a, 36 b, 37 a, 37 b and 37 c are diagrams showing the problemsIn the past. In FIG. 36 a, a case when the auxiliary protrusion 20 c isprovided on the CF substrate of the resin overlaying BM method is shown.FIG. 36 a shows a cross section at a line I-I in FIG. 34. On the TFTsubstrate, the drain bus line 12 is formed on the glass substrate 24,the drain bus line 12 is covered with an insulation film 30, and thepixel electrode 1S further formed on the insulation film 30. Theinsulation film 30 consists of a TFT gate insulation film, a protectionfilm covering the TFT and the like. Hitherto, the width d1 of theauxiliary protrusion 20 c is equal to approximately 10 μm, the width d2where the auxiliary protrusion 20 c and the pixel electrode 16 overlapis designed to be approximately 4 μm.

However, if the auxiliary protrusion 20 c is formed on the CF substrateof the resin overlaying BM method with this design value, the thicknessof the protrusion material becomes thin at the angular portion of acolor resin, for example, in the angular portion of the green resin G.Since the common electrode 26 is formed on the surface of the greenresin G of the angular portion, the electric line of force headingoutwards from the display area concentrates, and the liquid crystalmolecules become a state of alignment defect due to the electric fieldin this portion. Since the area of the alignment defect enters insidethe display domain, the similar dark portion as the alignment defectarea 40 in FIG. 32 is formed.

Further, besides the resin overlaying BM method described above, thereis a method using a black resin as the black matrix (hereinafter,referred to as a resin BM method). According to this resin BM method,the black resin is placed in the area forming the black matrix and eachresin is formed in an opening portion (display domain) so that the endportion of each resin overlaps the black resin. Therefore, as is thecase in the resin overlaying BM method, the level difference is formedand the similar problem described above occurs.

FIG. 36 b shows a case when other color filter shape is applied on theCF substrate, in which a chrome shading film 34 is formed as the blackmatrix and the color filter is formed on the shading film 34 bypatterning the color resin. In this case, the width d1 of the auxiliaryprotrusion 20 c is also equal to approximately 10 μm and the width d2where the auxiliary protrusion 20 c and the pixel electrode 16 overlapis also designed to be approximately 4 μm. As shown in FIG. 36 b, whenformed according to the design value, the concentration of electriclines of force heading outwards from the display area is suppressed, thealignment of the liquid crystal molecules is stabilized and the displaybecomes favorable. However, at the stage when a product is actuallyfabricated, various irregularities during the fabrication occur, and inmany cases, desired characteristics are not obtained.

FIGS. 37 a, 37 b and 37 c are diagrams showing problems of misalignmentin lamination and shot unevenness as irregularities during thefabrication. FIG. 37 a shows a case in which a misalignment occurs whenthe CF substrate and the TFT substrate are laminated, and the width d1of the auxiliary protrusion 20 c is equal to approximately 10 μm as isthe case in FIG. 36 b. However, in FIG. 37 a, the TFT substrate isdeviated in an upper right direction to the CF substrate in the diagram,thereby resulting in the width d2 where the auxiliary protrusion 20 cand the pixel electrode 16 overlap by approximately 3 μm. Therefore, thecontrol power to the liquid crystal molecules is weakened and, aninfluence from the lateral electric field caused by the drain bus lineat the end portion of the pixel electrode 16 occurs, therefore thealignment defect area as indicated by the hatched portion in the diagramoccurs. However, in the case of FIG. 37 a, the alignment defect area isunder the auxiliary protrusion 20 c and does not affect the display. Itwill be noted that when a misalignment in lamination occurs, theopposing width becomes wider at one end portion of the correspondingpixel electrode and the width becomes narrow at the other end portion.That is, in order to have a sufficient opposing width at thecorresponding end portions, a margin for laminating extremely reducesand fabrication also becomes difficult.

At this time, as shown in FIG. 37 c, exposure and the like are performedby dividing the display domain of a single panel into a plurality ofdivided areas SA-SD . . . when fabricating the liquid crystal display(liquid crystal panel). Therefore, the same display characteristics canbe obtained within each divided area SA-SD . . . . However, when thereare deviations or the like during exposure, display characteristics maybe different from other divided areas.

FIG. 37 b shows other divided area in the same panel as FIG. 37 a andshows a case when shot irregularities occur during exposure. In FIG. 37b, since irregularities occur when patterning the pixel electrode 16,although the distance d3 from the end face of the color resin B to theend face of the pixel electrode is supposed to be equal to 7 μmaccording to the original design value as shown in FIG. 37 a, thedistance d5 in FIG. 37 b is equal to 7.5 μm. Therefore, the width d4where the auxiliary protrusion 20 c and the pixel electrode 16 overlapbecomes to be equal to 2.5 μm and the alignment defect area indicated bythe hatched portion occurs. Furthermore, the alignment defect areaappears in the display domain instead of being hidden by the auxiliaryprotrusion 20 c. Therefore, in FIG. 37 b, the alignment defect area 40as shown in FIG. 32 occurs in the display domain.

In FIG. 37 c, if the divided area SA is an area where the pixelelectrode 16 is formed in the position in accordance with the designstandard as shown in FIG. 37 a and the divided area SB is an area wherethe position of the pixel electrode 16 is deviated from thepredetermined position due to shot irregularities as shown in FIG. 37 b,although a desired bright display is performed in the divided area SAwhen a certain display is performed, the alignment defect area occurs inthe divided area SB, thereby resulting in a dark display. In otherwords, an irregular shot phenomenon occurs.

FIG. 38 is a diagram showing the relationship between the design valueof the overlapping width (opposing width) and the generation ratio ofshot irregularities in which the overlapping width between the auxiliaryprotrusion and the pixel electrode. Here, an attention should be paidthat the design value of the overlapping width on the lateral axis isnot the overlapping width inside the actual panel. Even if the panel isfabricated according to a certain design value, irregularities ofseveral μm due to a misalignment of lamination between an upper andlower substrates, inaccuracy of the pattern for the structure(protrusion, color resin for color filter, etc.) formed on the substrateor the influence from the divided areas described above occur inside theactually fabricated panel. Therefore, the value of the overlappingwidth, when the whole display domain is viewed, is in a certain range.In this case, the alignment defect area appears inside the displaydomain in the portion where the overlapping width is small and thedifference in brightness partially occurs in the whole display domain.In such a case, shot irregularities are considered to have occurred atthe design value.

When observing this, if the design value of the overlapping width, inother words, if the design center is equal to approximately 4 μm, theirregularity in shooting occurs at a ratio of substantially 50%. Therange of the values for the actual overlapping widths in this case isconsidered to vary from approximately 1 μm to 7 μm. If the design centeris equal to approximately 6 μm, the shot irregularities are almosteliminated. The overlapping width in this case is considered to varyfrom approximately 3 μm to 9 μm.

Thus, in the MVA liquid crystal display in the past, as is the caseusing the color filter of the resin overlaying BM method or the resin BMmethod, a problem that many display defects in which brightness reducesoccurs when there is a large level difference on the substrate. Further,there is a problem that poor yield caused by extremely small margin infabrication exists as is the case because a display defect is easilycaused by slight irregularities in fabrication.

Therefore, an object of the present invention is to provide a liquidcrystal display which is high in brightness and has preferable displaycharacteristics and its fabrication method.

Another object of the present invention is to provide a liquid crystaldisplay with large margin in fabrication, high yield, and preferabledisplay characteristics and its fabrication method.

SUMMARY OF THE INVENTION

According to the first aspect of the present invention, the abovesubjects can be solved by a liquid crystal display having the followingdistinctive feature:

That is to say, a liquid crystal display comprises a first substratehaving a first electrode, a second substrate having a second electrodecorresponding to a pixel, liquid crystal having negative dielectricanisotropy sealed between the first and the second substrates, astructure which is provided on at least the first substrate to controlan alignment of the liquid crystal, and wherein the structure on thefirst substrate has a linear protrusion structure, an auxiliaryprotrusion structure extending from the protrusion structure andopposing to each of facing end portions of the second electrode, and awidth of the auxiliary protrusion structure wider than a width of theprotrusion structure.

According to the first aspect of the present invention, since the widthof the auxiliary protrusion facing the second electrode is more than 6μm at each corresponding end portion of the second electrode, analignment defect area does not appear inside the display domain and abright and preferable display with no reduction in brightness ispossible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIGS. 2 a and 2 b are diagrams showing an action of the presentinvention.

FIG. 3 is a diagram showing a second embodiment of the presentinvention.

FIG. 4 is a diagram showing a cross section at a line II-II in FIG. 3.

FIGS. 5 a, 5 b and 5 c are diagrams showing a structure of a spacerlessCF.

FIG. 6 is a diagram showing a third embodiment of the present invention.

FIG. 7 is a diagram showing a cross section at a line I-I in FIG. 6.

FIGS. 8 a and 8 b are diagrams showing a problem point of the structureof the spacerless CF shown in FIGS. 5 a, 5 b and 5 c.

FIG. 9 is a diagram showing a problem point of the structure of thespacerless CF shown in FIGS. 5 a, 5 b and 5 c.

FIG. 10 is a diagram showing a fourth embodiment of this invention.

FIGS. 11 a and 11 b are diagrams showing a cross section at a line C-C′in FIGS. 8 a and 8 b.

FIGS. 12 a, 12 b, 12 c and 12 d are diagrams showing a fabricationmethod of a liquid crystal display in an example according to the fourthembodiment of the present invention.

FIG. 13 is a diagram showing an other example according to the fourthembodiment of the present invention.

FIGS. 14 a, 14 b, 14 c and 14 d are diagrams showing a fabricationmethod of a liquid crystal display in the other example according to thefourth embodiment of the present invention.

FIGS. 15 a, 15 b and 15 c are diagrams showing a still another exampleaccording to the fourth embodiment of the present invention.

FIGS. 16 a and 16 b are diagrams showing an example according to a fifthembodiment of the present invention.

FIGS. 17 a and 17 b are diagrams showing an other example according tothe fifth embodiment of the present invention.

FIGS. 18 a through 18 f are diagrams showing a cross sectional view of aprocess describing a fabrication method of a liquid crystal displayaccording to a sixth embodiment of the present invention.

FIG. 19 is a diagram showing a cross sectional view of the processdescribing the fabrication method of the liquid crystal displayaccording to the sixth embodiment of the present invention.

FIG. 20 is a diagram showing a cross sectional view of the processdescribing the fabrication method of the liquid crystal displayaccording to the sixth embodiment of the present invention.

FIG. 21 is a diagram describing an issue to be solved by a seventhembodiment of the present invention.

FIG. 22 is a diagram describing the issue to be solved by the seventhembodiment of the present invention.

FIGS. 23 a and 23 b are diagrams showing the seventh embodiment of thepresent invention.

FIG. 24 is a diagram showing the seventh embodiment of the presentinvention.

FIG. 25 is a diagram showing an example of an effect according to theseventh embodiment of the present invention.

FIG. 26 is a diagram describing an issue to be solved by an eighthembodiment of the present invention.

FIG. 27 is a diagram showing a cross section at a line A-A in FIG. 26.

FIG. 28 is a diagram describing the eighth embodiment of the presentinvention.

FIG. 29 is a diagram showing a cross section at a line B-B in FIG. 28.

FIG. 30 is a diagram describing the eighth embodiment of the presentinvention.

FIG. 31 is a diagram showing a cross section at a line C-C in FIG. 30.

FIG. 32 is a diagram showing a basic structure of an MVA liquid crystaldisplay.

FIGS. 33 a through 33 c are diagrams showing a theory of the MVA liquidcrystal display.

FIG. 34 is a diagram showing the MVA liquid crystal display providedwith an auxiliary protrusion in the past.

FIGS. 35 a and 35 b are diagrams showing an action of the auxiliaryprotrusion.

FIGS. 36 a and 36 b are diagrams showing a problem point in the past.

FIGS. 37 a, 37 b and 37 c are diagrams showing a problem point in thepast.

FIG. 38 is a graph showing an occurrence rate of shot irregularities.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are described below with referenceto diagrams.

FIG. 1 shows a first embodiment of the present invention and isaccording to the first aspect of the present invention.

With reference to FIG. 1, a MVA liquid crystal display 100 is an activematrix type liquid crystal display provided with a switching device anda thin film transistor (hereinafter, referred to as a TFT) 14 at eachpixel and there are a red pixel R, a green pixel G and a blue pixel B asthe pixels so that color display can be performed. FIG. 1 shows one ofthe pixels and its peripheral portion.

On a TFT substrate where a TFT 14 is provided, wirings of a gate busline 10 partially serving as a gate electrode for the TFT 14 and a drainbus line 12 are formed. The TFT 14 consists of a drain electrode 12Dextending from a drain bus line 12, a source electrode 12S placedopposing to the drain electrode 12D, the drain electrode 12D of the gatebus line 10 and a part overlapping the source electrode 12S. Further,although not shown, a channel layer made of, for example, a-Si film isformed on the gate bus line. Furthermore, a pixel electrode 16 connectedto the source electrode 12S is formed on the TFT substrate. In the pixelelectrode 16, a slit 18 is provided diagonally to the pixel in thediagram and this slit 18 becomes a structure which controls thealignment of the liquid crystal on the substrate side. A connectingportion 16 a is provided at the pixel electrode 16 so that the pixelelectrode 16 is not electrically separated by the slit 18. In thismanner, a pixel electrode in a single pixel is electrically connected.

On a CF substrate where a color filter not shown is formed, a protrusion20 which is to be a structure to control the alignment of the liquidcrystal on the CF substrate side is provided diagonally to the pixel,and controls the alignment of the liquid crystal along with the slit 18on the TFT substrate. The slit 18 and the protrusion 20 are placedalternately when viewed in the plane. Further, an auxiliary protrusion20 a is formed to extend out of the protrusion 20 along the end portionof the pixel electrode 16. The auxiliary protrusion 20 a is formed byextending out of the protrusion 20 at a side, where the protrusion 20and a pixel electrode 20 a form an obtuse angle, at the part where theprotrusion 20 intersects the pixel electrode 16 when viewed in theplane.

For example, when the MVA liquid crystal display 100 is an XGA LCD panelwhich has a diagonal distance of 15 inches, the size of a single pixelis equal to 99 μm×297 μm, the widths of the slit 18 and the protrusion20 are equal to 10 μm respectively, and the distance between the slit 18and the protrusion 20 when viewed in the plane is equal to 25 μm.Further, the width of the connecting portion 16 a of the pixel electrode16 is equal to 4 μm and the distance between the end portion of thedrain bus line 12 and the end portion of the pixel electrode 16 is equalto 7 μm.

The point which makes the MVA liquid crystal display 100 shown in FIG. 1different from an MVA liquid crystal display 140 is the arrangement ofthe auxiliary protrusion 20 a. The auxiliary protrusion 20 a of the MVAliquid crystal display 100 is formed by entering inside a display domainin comparison with an auxiliary protrusion 20 c of the MVA liquidcrystal display 140. Here, the display domain means an opening of thepixel and the area where a light actually transmits. Although not shownin FIG. 1, a black matrix is formed on the CF substrate having theprotrusion 20 and the end face of the black matrix and the end face ofthe pixel electrode 16 are formed so that they substantially coincidewith each other, and in FIG. 1, an borderline of the pixel electrode 16(The borderline is a borderline on an assumption that the slit 18 doesnot exist. The same thing applies below.) becomes a visible outline ofthe display domain. In FIG. 1, all the auxiliary protrusions 20 a areformed so that the width between the auxiliary protrusion 20 a and theopposing pixel electrode 16 becomes equal to approximately 8 μm.

FIG. 2 a is a cross sectional view at a line I-I in FIG. 1 and shows anaction according to the structure in FIG. 1. A resin overlaid BM typecolor filter is formed on the CF substrate, a blue resin B is formed onthe glass substrate 22, and at the portion where the black matrix isformed, a green resin G is formed by overlaying on the blue resin B.Further, the end face of the green resin G, which is to be the end faceof the black matrix, substantially coincide with the end face of thepixel electrode 16 formed on a glass substrate 24. Thus, a portion wherethe pixel electrode 16 is formed (including a slit 18 portion) is thedisplay domain.

The width d1 of the auxiliary protrusion 20 a is equal to approximately10 μm and the opposing width d2 between the auxiliary protrusion 20 aand the pixel electrode 16 is equal to 8 μm.

Further, since the auxiliary protrusion 20 a is formed sufficientlyinside (display domain side) in order to avoid an influence from anangular portion of the green pixel G, concentration of an electric lineof force toward an angular portion of color resin can be avoided and analignment defect area does not appear in the display domain. Therefore,a light and good display with a high brightness can be obtained.Furthermore, in the aforementioned example, the width d1 of theauxiliary protrusion 20 c is the same as the width of the protrusion 20which is equal to 10 μm However, the width of the auxiliary protrusion20 c is not limited to this and may certainly be, for example₇approximately 12 μm which is longer than the width of the protrusion 20.

FIG. 3 shows a second embodiment of the present invention and isaccording to the second aspect of the present invention.

With reference to FIG. 3, the points which make an MVA liquid crystaldisplay 110 different from the MVA liquid crystal display 100 in FIG. 1)are the position of an auxiliary protrusion 20 b and the shape of thepixel electrode 16 at the opposing portion to the auxiliary protrusion20 b.

In the MVA liquid crystal display 110, the auxiliary protrusion 20 b isformed at the borderline of the pixel electrode 16, in other words, 6 μminside the visible outline of the display domain. Further, anoverhanging portion 16 c extending beyond the borderline of the pixelelectrode 16 is formed at a portion where the pixel electrode 16 facesthe auxiliary protrusion 20 b. The overhanging amount of the overhangingportion 16 c becomes equal to 2 μm. Therefore, an opposing width betweenthe auxiliary protrusion 20 b and the pixel electrode 16 becomes equalto 8 μm which provides a sufficient opposing width. Compared with thefirst embodiment, although the opposing widths are the same and equal to8 μm, the auxiliary protrusion 20 b does not enter the display domain,thereby reducing an occupied area of the auxiliary protrusion 20 b atthe display domain and increasing an aperture ratio more. Thiscontributes to an increase in brightness.

Further, a slit is composed of a collection of short slits 18 in the MVAliquid crystal display 110. A connecting portion 16 b of the pixelelectrode 16 is formed between the slits 18. A structure to control thealignment is thus formed by a plurality of unit structures to stabilizethe alignment of liquid crystal molecules on the structure, and tocreate a higher brightness and a quick response time can be improved.

FIG. 2 b is a cross sectional view at a line I-I in FIG. 3 and shows anaction according to the structure in FIG. 3. A color filter using achrome shading film as the black matrix is formed on the CF substrate.The width d1 of the auxiliary protrusion 20 b and the opposing width d2between the auxiliary protrusion 20 b and the pixel electrode 16 areequal to 10 μm and 8 μm respectively as is the case of the firstembodiment. However, since the pixel electrode 16 has the overhangingportion 16 c extending beyond the display domain, the width of theauxiliary protrusion 20 b entering the display domain is reduced.

With reference to FIG. 4 which is a cross sectional view at a line II-IIin FIG. 3, a detailed description follows. Although not shown, a gateelectrode made of aluminum and the like is formed on the glass substrate24 on the TFT substrate side, and a gate insulation film 36 is formedapproximately to 400 nm in thickness on the gate electrode. A drain busline 12 is formed approximately to 150-350 nm in thickness on the gateinsulation film 36 and a protection film 30 covering the TFT is formedapproximately to 330 nm in thickness on the drain bus line 12. An ITO(indium tin oxide) which is to be the pixel electrode 16 is formedapproximately to 50-150 nm in thickness on the protection film 30 and analignment film 32 covering the protection film 30 and the pixelelectrode 16 is formed approximately to 30-120 nm in thickness.

Further, a chrome shading film 34 is formed to approximately 100-200 nmin thickness on the glass substrate 22 on the CF substrate side andcolor resins R, G and Bare formed to approximately 0.9-2.5 μm each inthickness. The ITO which is to be a common electrode 26 is formed toapproximately 50-150 nm in thickness on the color resins R, G and B, andan alignment film 28 is formed to approximately 30-120 nm in thicknesson the ITO. It will be noted that the protrusion 20 and the auxiliaryprotrusion 20 b are formed on the common electrode 26, covered by thealignment film 28, and have the height of approximately 1.2-1.8 μm.

An end face of the pixel electrode 16 excluding the overhanging portion16 c of the pixel electrode 16 substantially coincides with an end faceof the chrome shading film 34 and the distance d1 between the drain busline 12 and the pixel electrode 16 is equal to 7 μm. Further, theoverhanging portion 16 c of the pixel electrode 16 extends 2 μm out ofthe display domain. Therefore, the distance d2 between the drain busline 12 and the overhanging portion 16 c is equal to 5 μm and theoverlapping width d3 with the chrome shading film 34 is 2 μm.Furthermore, the width of the auxiliary protrusion 20 b overhanging onthe display domain is equal to 6 μm and as a consequence, an opposingwidth between the auxiliary protrusion 20 b and the pixel electrode 16is 8 μm. So, the width of the auxiliary protrusion 20 b entering thedisplay domain is reduced as well as light and good display with a highbrightness can be obtained, thereby improving the aperture ratio.

It will be noted that if the width of the overhanging portion 16 c ismade larger, the auxiliary protrusion 20 b on the CF substrate side isnot required to be formed. That is because since an alignment defectarea occurs slightly inside the end portion of the pixel electrode 16,when the extending width becomes larger, even if the alignment defectarea occurs, the alignment defect area appearing in the display domaincan be suppressed.

FIGS. 5 a, 5 b and 5 c show an example of a structure of the CFsubstrate and shows a technology in which a protrusion structure isoverlaid on a resin overlaying BM method to serve also as a spacer(hereinafter, referred to as a spacerless CF). A CF substrate using thisspacerless CF can be applied to the first and second embodiments and athird embodiment to be described below. In FIG. 5 a, hatching portionsare portions each of color resin R, G and B is formed and functions as acolor filter. Other portions are overlaid by color resins and functionas the black matrix. The protrusion 20 is formed thereon. FIG. 5 b is across sectional view at a line A-A′ in FIG. 5 a. As shown in FIG. 5 b,two color resins are overlaid between each linear pixel to form theblack matrix BM. Further, FIG. 5 c is a cross sectional view at a lineB-B′ in FIG. 5 a. While portions other than lattice points become theblack matrix BM by overlaying two color resins, three color resins areoverlaid at the lattice points and furthermore, a protrusion 20 c whichis a part of the protrusion 20 is overlaid thereon and the protrusion 20c functions as the spacer.

FIG. 6 is a third embodiment of the present invention and is accordingto the third aspect of the present invention.

With reference to FIG. 6, the points which make an MVA liquid crystaldisplay 120 different from the MVA liquid crystal display 110 in FIG. 3are that an auxiliary protrusion is not formed and a shape of the pixelelectrode 16 at a portion where an auxiliary protrusion is formed in theother embodiments.

In the MVA liquid crystal display 120, the auxiliary protrusion is notformed. Instead, an overhanging portion 16 d extending beyond thedisplay domain and extending to above the drain bus line 12 which is thewiring is formed at the pixel electrode 16. The overhanging portion 16 dis formed by extending an end portion where the pixel electrode 16 andthe protrusion 20 form an obtuse angle, beyond the display domain, in anarea decided by the slit 18 arranged substantially in parallel and endportions of the protrusion 20 and the pixel electrode 16. In otherwords, the overhanging portion 16 d is a pixel electrode portionadjacent to an area where the alignment defect area 40 occurs in the MVAliquid crystal display 130 in FIG. 32.

With reference to FIG. 7 which is a cross sectional view at a line I-Iin FIG. 6, a detailed description follows. First, in this embodiment, anauxiliary protrusion is not formed on the CF substrate side. On the TFTsubstrate side, a gate insulation film 36 is formed on the glasssubstrate 24 and the drain bus line 12 to be wiring is formed there.Further, a planarized film 38 which is made of acrylic resin and thelike and serves also as a protecting film for the TFT is formed. Thepixel electrode 16 and the alignment film 32 are formed on theplanarized film 38. An end face of the pixel electrode 16 other than theoverhanging portion 16 d of the pixel electrode 16 substantiallycoincides with an end face of the chrome shading film 34. Furthermore,the overhanging portion 16 d of the pixel electrode 16 extends 9 μmbeyond the display domain (in other words, overlapping of 9 μm with thechrome shading film 34 exists), and overlapping of 2 μm with the drainbus line 12 via the planarized film 38 exists. By structuring in thismanner, the end portion of the pixel electrode 16 can be arranged at aposition sufficiently apart from the display domain. Also, since thethick planarized film 38 is between the overhanging portion 16 d and thedrain bus line 12, an influence from the drain bus line 12 can bereduced. Thus, even if the alignment defect area occurs in adjacent tothe end portion of the overhanging portion 16 d, the alignment defectarea occurs sufficiently apart from the display domain and does notaffect the display. Hence, the light and good display with a highbrightness can be obtained and since an arrangement of the auxiliaryprotrusion is not required, the aperture ratio can also be improved.

It will be noted that, in this embodiment, the auxiliary protrusion maybe formed on the CF substrate side. In that case, consideration may begiven to a position to form the auxiliary protrusion so that aninfluence given to the aperture ratio is reduced.

Although the present invention is described above in detail, the presentinvention is not limited to the above embodiments and can be deformed toan extent the present invention is not deviated.

It will be noted that, in the present invention, the following structuremay also be distinctive features:

(1) A first substrate is the CF substrate and a first electrode is thecommon electrode.

(2) A second substrate is the TFT substrate and a second electrode isthe pixel electrode.

(3) In the above structure (2), a structure of the second substrate isthe slit to be formed in the pixel electrode.

(4) A structure to control the alignment of the liquid crystal on thefirst and the second substrate is arranged in an inclined fashionagainst the pixel.

(5) In the above structure (4), inclined directions against the pixelare at least two directions in a single pixel.

(6) The width of the auxiliary protrusion is equal to approximately 10μm and the opposing width is equal to approximately 8 μm.

(7) The width the second electrode extends is more than 2 μm.

(8) In the above structure (1), a shape is formed by a level differenceformed by overlaying resins and the auxiliary protrusion is formed atthe portion of the level difference exists.

(9) In the above structure (8), the black matrix is formed by overlayingcolor resins provided at each pixel.

(10) In the above structure (8), a black resin to be the black matrix isprovided and the end portion of color resins provided at each pixel isoverlapped with the black resin.

(11) In the above structure (8), the distance between an end face of theportion where the level difference exists and the end portion of theauxiliary protrusion is more than 6 μm.

Next, the liquid crystal display according to the fourth embodiment ofthe present invention is described with reference to FIG. 8 a throughFIG. 15 c. This embodiment is according to the third aspect of thepresent invention and has a distinctive feature in which the structureof the CF substrate described with reference to FIGS. 5 a, 5 b and 5 cin the second embodiment is further improved.

The CF substrate shown in FIGS. 5 a, 5 b and 5 c forms the color resinsR, G and B at each pixel and forms the black matrix BM by overlaying twoor three layers of color resins R, G and B in the shaded areas betweenthe pixels. And after forming the common electrode 26 by depositing theITO, the protrusion 20 to control an alignment direction is formed.

Although FIG. 8 a is the same as FIG. 5 a shown, FIG. 8 a more clearlyshows overlaying of the color resins R, G and B in the shaded areas ofthe CF substrate. FIG. 8 b shows a cross sectional view cut at a lineC-C′ in FIG. 8 a. As shown in FIGS. 8 a and 8 b, the BM is formed byoverlapping the color resin layers of the adjacent pixels between thepixels, and the width of the auxiliary protrusion 20 a formed along anextending direction of the BM extends from a top of the BM to a top ofthe color resin layers of the pixel opening portions.

However, the level difference exists at the BM and the color resinlayers at the pixel opening portions, and the auxiliary protrusion 20 aformed by stepping over this difference may cause a problem in which apattern thickness becomes too thin at the portion having the leveldifference or the pattern remains only leaves on the BM but not on thepixel opening portions during its formation process, as shown in a rangeβ in FIG. 8 b.

FIG. 9 shows the state in which the CF substrate having the auxiliaryprotrusion 20 a cut at the portion having level difference and the TFTsubstrate are laminated. When the auxiliary protrusion 20 a to begradually formed from the BM to the pixel opening portions is thinned ordisconnected as shown in FIG. 9, the alignment defect area occurs due toan electric field generated between the common electrode 26 on the CFsubstrate side at the portion having the level difference and the pixelelectrode 16 on the TFT substrate side. If this alignment defect areaoccurs, the display becomes dark or the display irregularities occur,thereby reducing the quality of the display.

In order to solve this problem, in this embodiment, overlaying of colorresins to form the BM is not performed at the area the auxiliaryprotrusion 20 a arranged along the end side of pixel electrode 16, andonly one layer of the color resin R, G or B is formed, or a color layeris not formed in the formation area.

With reference to FIG. 10 through FIG. 12 d, a structure and afabrication method are described as an example of the liquid crystaldisplay according to this embodiment. FIG. 10 shows a distinctivefeature of this embodiment by corresponding to FIG. 9. As shown in FIG.10, in this example, the level difference at the lower layer in the areathe auxiliary protrusion 20 a is formed is eliminated by overlaying onlyone layer (color resin layer B in the diagram) of color resin layerbelow the auxiliary protrusion 20 a. In order to realize this, the endportion of the BM at the lower layer in the area the auxiliaryprotrusion 20 a is formed, in other words, the end portion of theoverlaid area of two color resins is moved back to the area between thedrain bus line 12 and the pixel electrode 16 without coinciding with theend portion of the pixel electrode 16 of the TFT substrate, and only onecolor resin layer is formed below the area the auxiliary protrusion 20is formed.

FIG. 11 a is an enlarged view showing this example corresponding to theblock a shown in FIG. 8 a. FIG. 11 b shows inside the block a applied asa comparison before this embodiment is applied. As shown in FIG. 11 a, aplanarized area 21R, where only the color resin layer R is formed, isformed at the lower layer in the area the auxiliary protrusion 20 a isformed along the end portion of the color resin R, and a planarized area21G, where only the color resin layer G is formed, is formed at thelower layer in the area the auxiliary protrusion 20 a is formed alongthe end portion of the color resin G.

Due to the existence of these planarized areas where the leveldifference is eliminated, the auxiliary protrusion 20 a shown in FIG. 10can be formed to a predetermined thickness and into a predeterminedshape. Therefore, even if the alignment defect occurs when the liquidcrystal at the end portion of the pixel electrode 16 is affected by alateral electric field from the drain bus line 12, occurrence of thealignment defect area in the display domain can be prevented. Further,since the auxiliary protrusion 20 a arranged in parallel with the endside of the pixel electrode 16 controls the direction of the liquidcrystal molecules toward a direction where light leakage does not occur,no shading is required in this area. Furthermore, as shown in FIG. 10,since the level difference in the ITO film of the common electrode 26produced by overlaying a color resin is apart from the pixel electrode16 on the TFT substrate, the influence to the display domain caused byan abnormal electric field due to the level difference in the ITO filmcan be ignored.

Next, with reference to FIGS. 12 a through 12 d, a fabrication method ofthe liquid display in which the above-planarized area is formed isdescribed. FIG. 12 a shows a part of an MR pattern of the color resinlayer R formed at a predetermined position on the CF substrate. Thecolor resin layer R is formed in a hatched portion in the diagram.Notches 21B′ and 21G′ cut out into a pattern shape of the planarizedarea are respectively formed at their own predetermined positions on theend side in the vertical direction in the diagram of the color resinlayer R in order to form the planarized area.

Further, FIG. 12 b shows a part of an MG pattern of the color resinlayer G formed at a predetermined position on the CF substrate, and thecolor resin layer G is formed in the hatched portion in the diagram.FIG. 12 c shows a part of an MB pattern of the color resin layer Bformed at a predetermined position on the CF substrate and the colorresin layer B is formed in the hatched portion of the diagram. Notches21R′, 21G′ and 21B′ cut out into a pattern shape of the planarized areaare also formed at their own predetermined positions on end sides In thevertical direction of the diagrams of the color resin layers G and B inorder to form the planarized areas.

By aligning and patterning each of color resin layers R, G and Baccording to the patterns MR, MG and MB, as shown in FIG. 12 d, thecolor resins R, G and B are alternately formed at each electrode, and acolor filter where planarized areas 21R, 21G and 21B are formed atpredetermined positions and the BM are formed. Further, the thickness ofeach color resin layer is approximately 1.5 μm.

Next, the ITO film with a thickness of 100 nm is deposited by a masksputtering and the common electrode 26 is formed, and then theprotrusion 20 and the auxiliary protrusion 20 a for alignment controlare formed to 1.5 μm in thickness. Since the auxiliary protrusion 20 ais formed on the planarized areas 21R, 21G and 21B, the thickness of theauxiliary protrusion 20 a is not reduced nor separated.

A vertical alignment film 28 is formed to approximately 80 nm inthickness on the CF substrate where a main portion has been formed inthis manner. On the other hand, a vertical alignment film 32 is coatedinto 80 nm in thickness on the TFT substrate where the pixel electrode16, having the gate bus line 10, the drain bus line 12, the TFT 14 andthe slit 18 for alignment control, is formed. The TFT substrate and theCF substrate are laminated by using a sealant. At this time, the gapbetween the two substrates is obtained by a 4-layer pillar of colorlayers R, G, B and the protrusion layer and is maintained at 4 μm inheight. The liquid crystal display is completed by pouring the negativetype liquid crystal into this gap and arranging polarizing plates onboth sides of the substrates in cross-Nicol.

Next, with reference to FIGS. 13 through 14 d, another example of theliquid crystal display according to this embodiment is described. Inthis embodiment, not only the level difference is eliminated at thelower layer in the area the auxiliary protrusion 20 a is formed bymaking only one resin layer below the auxiliary protrusion 20 a, butalso a planarized area is formed at a lower layer of the protrusion 20intersecting the BM by expanding the planarized area further.

FIG. 13 is an enlarged view showing this example corresponding to theblock a shown in the FIG. 8 a. As shown in FIG. 13, a planarized area21R is formed, where only the color resin layer R is formed, at thelower layer of the formation area of the auxiliary protrusion 20 a whichis along the end portion of the color resin layer R of the intersectionportion between the BM and the protrusion 20.

A planarized area 21G, where only the color resin layer G is formed, isformed at the lower layer of the formation of the auxiliary protrusion20 a which is along the end portion of the color resin layer G and ofthe intersection portion between the BM and the protrusion 20.

Due to the existence of these planarized areas of 21R and 21G where thelevel difference is eliminated, the protrusion 20 intersecting the BMand the auxiliary protrusion 20 a can be formed into a predeterminedshape with a predetermined thickness without generating the leveldifference. Further, a cross section of adjacent to the auxiliaryprotrusion 20 a according to this example is similar to the one shown inFIG. 10.

Therefore, even if the alignment defect occurs when the liquid crystalat the end portion of the pixel electrode 16 is affected by the lateralelectric field due to the drain bus line 12, occurrence of the alignmentdefect area in the display domain can be prevented. Further, since theauxiliary protrusion 20 a arranged in parallel with the end side of thepixel electrode 16 controls the direction of the liquid crystal moleculetoward a direction where light leakage does not occur, no shading isrequired in this area. Furthermore, as is the case shown in FIG. 10,since the level difference in the ITO film of the common electrode 26produced by overlaying a color resin is apart from the end portion ofthe pixel electrode 16 on the TFT substrate, the influence to thedisplay domain caused by an abnormal electric field due to the leveldifference in the ITO film can be ignored. Also, since the leveldifference between the protrusion 20 and the auxiliary protrusion 20 ais eliminated, the level difference is eliminated at the ITO film of thecommon electrode 26, thereby performing the alignment control in thisarea even more stably. Further, since shading in this area is controlledin the alignment by the auxiliary protrusion 20 a and a light leakagedoes not occur adjacent to the drain bus line 12, a reduction incontrast and the like do not occur.

FIGS. 14 a through 14 d show a fabrication method of a liquid crystaldisplay in which the above-referenced planarized area is formed. FIG. 14a shows a part of the MR pattern of the color resin layer R formed at apredetermined position on the CF substrate. The color resin layer R isformed in the hatched portion in the diagram. FIG. 14 b shows a part ofthe MG pattern of the color resin layer G formed at a predeterminedposition on the CF substrate, and the color resin layer G is formed inthe hatched portion in the diagram. FIG. 14 c shows a part of the MBpattern of the color resin layer B formed at a predetermined position onthe CF substrate, and the color resin layer B is formed in the hatchedportion in the diagram.

The notches 21R′, 21B′ and 21G′ cut out into a pattern shape of theplanarized area are respectively formed at the predetermined positionson end sides in vertical direction in the diagram of the color resinlayers R, G and B in order to form the planarized areas.

Since the fabrication method of the liquid crystal display according tothis example is similar to the fabrication method described withreference to FIGS. 12 a through 12 d, the description is omitted.

Next, still another example of the liquid crystal display according tothis embodiment is described with reference to FIGS. 15 a, 15 b and 15c. A spacerless CF shown in FIGS. 15 a through 15 c is an example of astructure of the CF substrate and is similar to the spacerless CF shownin FIGS. 5 a, 5 b and 5 c. However, this structure has a distinctivefeature to simultaneously form a shading area by a black resin and theprotrusion 20 for alignment control after forming a stripe shape of eachcolor resin and the ITO film of the common electrode 26. According tothis structure, no level difference occurs in the ITO film and apreferable display can be obtained without forming the auxiliaryprotrusion 20 a.

The hatched portions in FIG. 15 a are the portions where color resin R,G and B are respectively formed and function as a color filter. Otherportion functions as the black matrix by overlaying color resins. TheITO film of the common electrode 26 is formed thereon, and the BM andthe protrusion 20 are formed on the ITO film. FIG. 15 b is a crosssectional view at a line A-A′ in FIG. 15 a. The common electrode 26 isformed on the surface of each color resin layer and the BM by the blackresin and the protrusion 20 are formed on the common electrode 26.Further, FIG. 15 c is a cross sectional view at a line B-B′ in FIG. 15a. Although the portion excluding the lattice points becomes the BM byoverlaying the black resin over a single color resin, resins of threecolors are overlaid on the lattice points and a protrusion 20 c which isa part of the protrusion 20 by the black resin is further overlaid andthe portion of the lattice points functions as the spacer. According toa structure like this, the level difference is eliminated on the wholesurface of the substrate of the ITO film of the common electrode 26,therefore the alignment control can be performed even more stably.

Next, a liquid crystal display according to a fifth embodiment of thepresent invention is described with reference to FIG. 16 a through FIG.17 b. This embodiment is according to the fourth aspect of the presentinvention.

While there are several methods of forming the vertical alignment filmon the CF substrate or the TFT substrate, the substrate is generallycleaned before forming the alignment film in any method. Foreignmaterials attached to the substrate are removed by cleaning, therebyreducing defects due to foreign materials when forming the alignmentfilm. There are a single-panel processing and a batch processing in thecleaning methods. After cleaning in both methods, the substrate is driedby an air-knife drying, a hot water pull-up drying and the like.

As shown in FIGS. 15 a through 15 c in the aforementioned forthembodiment, when forming the color resins into the strip shape (or anisland shape) for forming the color filter, a gap equal to approximately100 nm-10 μm is formed between adjacent color resins as shown by bRG,bGB and bBR in FIG. 15 b. In order to improve the flatness of the CFsubstrate, a planarization process is performed to fill this gap bycoating an overcoat resin on the CF substrate. However, since theplanarization process results in an increase in cost, the gap betweenthe color resins may not be filled.

In the liquid crystal display according to the MVA method, when the CFsubstrate where the gap remains between color resins is used, theprotrusion for alignment control is formed as to step over the gapbetween color resins. Usually, when cleaning the CF substrate beforeforming the alignment film, cleaning liquid runs along the gap betweenthe color resins during the drying process such as the air-knife drying,the hot water pull-up drying. At this time, if the protrusion is formedas to step over the gap, the cleaning liquid can not run along the gapand remains in the gap portion. If the alignment film is formed on theCF substrate in this state, an area where the alignment film is notcoated may occur at the remaining portion of the cleaning liquid, or avertical alignment nature may be lost. Since the liquid molecules cannotbe aligned properly in such area, display defect occurs.

So, in this embodiment, the above problem is solved by measuresdescribed below.

The first measure is to completely fill the gap by a protrusion materialto eliminate the cleaning liquid residue in the gap. As described above,since coating by the overcoating resin results in an increase in cost,in this embodiment, the gap is filled by the protrusion material insteadof overcoating. Thus, the gap is eliminated on the CF substrate, therebyrealizing uniform drying and avoiding the cleaning liquid residue.

The second measure is to secure the continuous gap as is the case beforeby selectively removing the protrusion material on the gap. Since achannel for the cleaning liquid is secured on the gap, the equivalentdrying effect as the case where the protrusion material is not formed onthe gap can be obtained.

By using this embodiment, while suppressing steps of the processes andan increase in cost, the cleaning liquid residue can be reduced duringdrying. In this manner, occurrence of the area where the alignment filmis not coated or the area where the thickness of the alignment film isthin can be reduced thereby realizing a high-quality liquid crystaldisplay without display defects.

A specific description with reference to examples is described below.

EXAMPLE 1

As shown in FIGS. 16 a and 16 b, color filter resins R,G and B areformed into a stripe shape on the CF substrate 22. At this time, gapsbRG and bGB equal to 10 μm are given between the resins. The commonelectrode 26 is formed on the CF substrate 22 and the protrusionmaterial is coated to 1.5 μm in thickness. By using a photolithographyprocess, the protrusion 20 is patterned into an intended form. At thistime, a photomask on which the pattern to selectively remove theprotrusion portions stepping over the gaps bRG and bGB between theresins is drawn is used. Thereby, the CF substrate 22 can be obtainedwithout protrusion materials on the gaps bRG and bGB. The CF substrate22 obtained in this manner is cleaned and dried by using the air-knife.At that time, the cleaning liquid attached to the CF substrate 22 isblown off by traveling through the gaps bRG and bGB between the resins.Then, the alignment film is formed by using a printing method. In thismanner, the CF substrate 22 without the area the alignment film is notcoated nor the area the thickness of the alignment film is thin can beformed. Then, the liquid crystal display is fabricated by the normalprocess. Thereby, a high-quality liquid crystal display without displaydefects can be obtained.

It will be noted, in this example, the protrusion material on the gapsbRG and bGB is not required to be completely removed. For example, whenthe width of the gap bRG or bGB is equal to 10 μm, only 5 μm of theprotrusion material may be removed and the remaining 5 μm may be lefton. In other words, sufficient continuous gaps for traveling thecleaning liquid is required to be secured.

EXAMPLE 2

As shown in FIGS. 17 a and 17 b, the color filter resins R, G and B areformed into a stripe shape on the CF substrate. At this time, the gapsbRG and bGB equal to 10 μm are preserved between the resins. The commonelectrode 26 1S formed on the CF substrate 22 and the protrusionmaterial is coated to 1.5 μm in thickness. By using the photolithographyprocess, the protrusion 20 is patterned into an intended form. At thistime, the photo mask on which the pattern to selectively leave theprotrusion material in all the gaps of bRG and bGB between resins isdrawn is used. Therefore, the CF substrate 22 where the gaps bRG and bGBare completely filled can be obtained. The CF substrate 22 obtained inthis manner is cleaned and dried by using the air-knife. At that time,the cleaning liquid attached to the CF substrate 22 is blown off bytraveling the surface of the CF substrate 22. Then, the alignment filmis formed by using the printing process. The area where the alignmentfilm is not coated or the area where the thickness of the alignment filmis thin does not occur on the CF substrate obtained in this manner.Then, the panel is completed by the normal process. Thus, a high-qualityliquid crystal display without display defects can be obtained.

It will be noted that, 1n the above examples 1 and 2, a shape of thecolor filter resin to be formed is not necessarily required to be thestripe shape. An island shape and other shapes are also allowed.

According to this embodiment, without resulting in an increase in stepsof the processes and in cost, occurrence of the area where the alignmentfilm is not coated due to the cleaning liquid residue and the area wherethe thickness of the alignment film is thin can be reduced, and a veryhigh-quality liquid crystal display with a very high visual field in apreferable alignment state can be fabricated without display defects.

Next, a fabrication method of the liquid crystal display according tothe sixth embodiment of the present invention is described withreference to FIG. 18 a through FIG. 20. This embodiment is according tothe fifth aspect of the present invention. This embodiment is afabrication method of the CF substrate and relates to a method offorming a spacer pattern and a protrusion pattern for alignment controlof the MVA on the color filter with a photosensitive material by usingphoto processing.

Hitherto, when forming the protrusion pattern and the spacer pattern bya photo processing using the photosensitive material, the photoprocessing is required to be used in two stages since the differencebetween the thickness of the protrusion and the thickness of the spaceris great.

Specifically, after coating, pre-baking, exposing, developing andpost-baking the photosensitive material (photo resist) on a substrate tobe processed in order to form the protrusion pattern, the same photoprocessing used to form the protrusion pattern is once again repeated toform the spacer pattern this time.

Thus, since the two similar process is performed because the thicknessof the protrusion and the spacer is different, the process islengthened, thereby causing problems of a reduction in yield and anincrease in cost. Therefore, if two kinds of patterns having differentfilm thickness can be formed on the substrate to be processed by onephoto processing, an increase in manufacturing yield and a reduction incost can be achieved.

This embodiment is specifically described below based on examples.

EXAMPLE 1

A case using a positive type photosensitive material is described.

FIG. 18 a shows a cross section of the CF substrate 22.

A color filter for color resins R, G and B is formed on the CF substrate22 corresponding to each pixel, and the common electrode 26 is formed onthe whole surface. It will be noted that, in this example, a chrome filmis used as the BM and the color filter is formed after patterning thechrome film on the CF substrate.

On a surface of the color filter on this CF substrate 22, the positivetype photosensitive material 50 is coated by a spinner so that thethickness becomes equal to 4.2 μm after pre-baking. A novolak type photoresist can be used as the positive type photosensitive material 50.

After pre-baking, the CF substrate 22 is put on a substrate stage of aproximity aligner, and a first mask (not shown) and the CF substrate 22are positioned and exposed based on the BM pattern. A pattern to shadeforming locations of the spacer portion and the protrusion portion isdrawn on the first mask. However, the width of shading at the forminglocation of the protrusion is widened by approximately 2 μm against thedesign value. Exposure is performed at an exposure value of h ν (1)which allows the photosensitive material 50 to be sufficiently removedat exposure points by developing (FIG. 15 b). In this example, h ν(1)=20 mJ/cm².

Further, by using the proximity aligner, the CF substrate 22 and asecond mask (not shown) are positioned based on the BM pattern andexposed. A pattern in which the forming location of the protrusionportion is not shaded is drawn on the second mask. However, the width ofan opening at the forming location of the protrusion portion is widenedby 3 μm on each side or approximately 6 μm in total against the width ofthe shading pattern for the protrusion portion on the first mask.Exposure is performed at the exposure value of h ν (2) which allows thefilm thickness of the photosensitive material 50 to remain byapproximately 1.5 μm by developing (FIG. 18 c). In this example, h ν(2)≈7 mJ/cm².

Next, the CF substrate 22 is developed by a developing solutioncontaining 2.38% of TMAH. After developing, the film thickness of thespacer 52 is 4.1 μm and the film thickness of the protrusion 20 is 1.5μm. After developing, post-baking (curing) is performed and the CFsubstrate for the MVA where the spacer 52 and the protrusion 20 areformed is completed. The film thickness after post-baking (filmthickness measured from the surface of the color filter) is 4.0 μm forthe spacer and 1.4 μm for the protrusion portion (FIG. 18 d). It will benoted that the order of exposure using the first mask and the secondmask can be reversed.

EXAMPLE 2

Next, the case using a negative type photosensitive material isdescribed.

First, the same CF substrate 22 shown in FIG. 18 a as in the case usingthe positive type photosensitive material described above is used.

On the surface of the color filter on this CF substrate 22, a negativetype photosensitive material 54 is coated by the spinner so that thethickness becomes equal to 4.2 μm after pre-baking. A novolak type photoresist can be used as the negative type photosensitive material 54.

After pre-baking, the CF substrate 22 is put on a substrate stage of aproximity aligner, and a third mask (not shown) and the CF substrate arepositioned and exposed based on the BM pattern. A pattern in which theforming location of the spacer portion is not shaded is drawn on thethird mask. Exposure is performed at an exposure value of h ν (3) whichallows the sufficient photosensitive material 54 to remain at exposurepoints by developing (FIG. 18 e). In this example, h ν (3)=20 mJ/cm².

Further, by using the proximity aligner, the CF substrate 22 and afourth mask (not shown) are positioned and exposed based on the BMpattern. A pattern in which the forming location of the protrusionportion is not shaded is drawn on the fourth mask. However, the width ofan opening at the forming location of the protrusion portion is widenedby approximately 4 μm against a design value. Exposure is performed atthe exposure value h ν (4) which allows the film thickness of thephotosensitive material 54 to remain by approximately 1.5 μm bydeveloping (FIG. 18 f). In this example, h ν (4)≈7 mJ/cm².

Next, the CF substrate 22 is developed by a developing solutioncontaining 2.38% of TMAH. After developing, the film thickness of thespacer 52 is 4.1 μm and the film thickness of the protrusion 20 is 1.5μm. After developing, post-baking (curing) is performed and the CFsubstrate for the MVA where the spacer 52 and the protrusion 20 areformed is completed. The film thickness after post-baking (filmthickness measured from the surface of the color filter) is 4.0 μm forthe spacer and 1.4 μm for the protrusion portion (FIG. 18 d). Further,the order of exposure using the third mask and the fourth mask can bereversed.

EXAMPLE 3

Next, by using the positive type photosensitive material, a method offorming the spacer 52 and the protrusion 20 by using only one mask andexposing only once is described by using the CF substrate 22 shown inFIG. 18 a.

As is the case in the Example 1, the positive type photosensitivematerial 50 is coated on the surface of the color filter on the CFsubstrate 22. After pre-baking, the CF substrate 22 is put on thesubstrate stage of the proximity aligner, and a fifth mask (not shown)and the CF substrate 22 are positioned and exposed based on the BMpattern.

A pattern which shades the forming location of the spacer is drawn onthe fifth mask. At the same time, a pattern in a semi-shaded state isalso drawn at the forming location of the protrusion portion to obtainsubstantially the exposure value of h ν (2) when the exposure value of hν (1) is obtained at the unshaded opening portion, and the width of thispattern is widened by approximately 2 μm against a design value.Irradiation is performed at the exposure value of h ν (1) which allowsthe photosensitive material 50 to be sufficiently removed at theexposure points by developing (FIG. 19).

In this way, the spacer 52 equal to 4.1 μm. In film thickness and theprotrusion 20 equal tom 1.5 μm in film thickness shown in FIG. 18 d canbe simultaneously formed by a single exposure.

EXAMPLE 4

Next, by using the negative type photosensitive material, a method whichforms the spacer 52 and the protrusion 20 by using only one mask andexposing once, is described by using the CF substrate 22 shown in FIG.18 a.

As is the case in the Example 2, the negative type photosensitivematerial 54 is coated on the surface of the color filter on the CFsubstrate 22. After pre-baking, the CF substrate 22 is put on thesubstrate stage of the proximity aligner, and a sixth mask (not shown)and the CF substrate 22 are positioned and exposed based on the BMpattern.

On the sixth mask, an opening pattern is drawn at the forming locationof the spacer. At the same time, a pattern in a semi-shaded state isalso drawn at the forming location of the protrusion portion to obtainsubstantially the exposure value of h ν (4) when the exposure value of hν (3) is obtained at the unshaded opening portion, and the width of thispattern is widened by approximately 4 μm against a design value.Irradiation is performed at the exposure value of h ν (3) which allowsthe photosensitive material 54 to sufficiently remain at the exposurepoints by developing (FIG. 20).

In this way, the spacer 52 equal to 4.1 μm in film thickness and theprotrusion 20 equal to 1.5 μm in film thickness shown in FIG. 18 d canbe simultaneously formed by a single exposure.

As described above, according to this embodiment, the spacer pattern andthe protrusion pattern for the MVA cannot be formed on the color filterof the substrate by performing one-cycle photo processing. Therefore, afabrication yield of the color filter substrate for the MVA with thespacer can be improved and also the cost for the device can be reduced.

The present invention is described in detail above. However, the presentinvention is not limited to the above-described embodiments anddeformations are possible to the extent not to deviate the presentinvention.

It will be noted that, in the present invention, the followingstructures can also be distinctive features.

(1) During the fabrication process of the CF substrate to be used tofabricate the MVA liquid crystal display, when forming the pattern forthe protrusion with the photosensitive material on the color filter byusing the photolithography process, the distinctive feature is that thepattern for the spacer is formed with the same photosensitive materialby using the same photolithography process.

By coating the photosensitive material (photoresist) during theformation of the protrusion pattern to the film thickness for formingthe spacer pattern which is thicker than the film thickness of theprotrusion and adjusting the exposure value, the patterns for theprotrusion and the spacer can be formed on the CF substrate by a singlephotolithography process.

Since the patterns for the protrusion and the spacer can be formed by atleast one cycle of the photo resist coating, pre-baking, developing andpost-baking, the fabrication yield of the CF substrate can be improvedand the cost can be reduced.

(2) The distinctive feature is that the exposure values irradiated onthe photosensitive material to form the patterns for the protrusion andthe spacer are different at the locations to form the protrusion portionand the spacer portion.

Since the protrusion pattern is thinner than the spacer pattern, adesired pattern cannot be formed by the same exposure value. Therefore,the exposure values irradiated on the photo resist at the protrusionportion and the spacer portion are made different. Since the coating isthe same, the film thickness of the photo resist in the areas formingthe protrusion and the spacer become substantially the same filmthickness at pre-baking. Therefore, by adjusting the exposure value forforming the protrusion portion and the spacer portion, the filmthickness of the protrusion portion and the spacer portion can beselectively varied by the same developing.

(3) The distinctive feature is to use two masks having the differentpatterns and to expose the photosensitive material on the CF substrateone by one with each mask. By using the two masks and exposing one byone with each mask, the exposure value to form the protrusion portionand the spacer portion can be varied.

(4) This case is when the photosensitive material in the exposure area(the area irradiation energy is transmitted) is the positive typephotosensitive material to be removed during the developing process, andthe distinctive feature is that, among the two masks used for exposure,the both patterns for the protrusion and the spacer (the pattern shadedby the mask) are formed on one mask and only the pattern for theprotrusion (the pattern not shaded by the mask) is formed on the othermask. In this way, the film thickness of each pattern can easily bevaried.

(5) The distinctive feature is that the protrusion pattern on the maskwhere only the pattern for the protrusion is drawn is larger than theprotrusion pattern on the mask where both patterns for the protrusionand the spacer are drawn. In order to cope with a situation in which analignment error occurs in the exposure using the second mask (the secondexposure) applied to the area where the exposure using the first mask(the first exposure) is performed, the protrusion pattern on the maskwhere only the pattern for the protrusion is drawn is made larger(wider) than the protrusion portion on the mask for the first exposure.Deviation in overlaying at the first exposure and the second exposuremay occur in spite of every possible measure taken, and there arepossibilities that shortness of the protrusion, accuracy of the locationof the protrusion and the film thickness of the protrusion portion areaffected. However, a measure for this problem can be possible by makingthe protrusion pattern on the mask with only the pattern for theprotrusion larger than the protrusion pattern on the mask with bothpatterns for the protrusion and the spacer.

(6) The fabrication method of the color filter and the mask used for thefabrication of the color filter are described in which the fabricationmethod has the distinctive feature in making the width of the protrusionpattern on the mask at the first exposure (exposure using the firstmask) wider than the design value in an anticipation of a variationamount when the width of the lines do not comply with the design due tothe double exposure (double exposure at periphery of the edge of theprotrusion portion). The width of the protrusion does not comply withthe design value due to the double exposure at periphery of theprotrusion portion when exposure is performed by using the two masksand, moreover, the masks as described in (5) above. Therefore, the widthof the protrusion on the mask used at the first exposure is made widerfor the peripheral double.

(7) When using the negative type photosensitive material to be removedfrom the unexposed area (the area irradiation energy is not transmitted)during the developing process, the distinctive feature is that each ofthe two masks used for exposure forms a pattern on each mask for theprotrusion or a spacer by each pattern. When the photosensitive materialforming the protrusion and the spacer is the negative type, the twomasks used for exposure form the patterns on the mask by each patternfor the protrusion or for the spacer. In other words, the pattern isformed on the CF substrate by the mask with only the protrusion patternand the mask with only the spacer pattern. When forming the pattern withthe negative type photosensitive material, the spacer portion is exposedso that substantially 100% of the photosensitive material remains bydeveloping and the protrusion portion is irradiated at the exposurevalue sufficient for forming the required film thickness. Thus, themasks used for the two exposures are the mask with only the protrusionpattern and the mask with only the spacer pattern.

(8) The distinctive feature is that patterns at the protrusion andspacer portion are patterned on the same mask and the protrusion and thespacer are formed on the CF substrate by a single exposure by using amask in which a transmissivity of the pattern for the protrusion on themask is suppressed so that the exposure value is reduced to some extentduring the exposure. In order to form the pattern for the protrusion andthe spacer pattern on a single mask (a single exposure), the mask wherethe transmissivity of the mask portion for the protrusion portion isreduced is used so that the exposure value for the forming area of theprotrusion is formed is lower than the actual exposure value. To exposeby a single mask (a single exposure), there is a method of making astructure to change the transmissivity (for example, forming a shadingfilm thin) so that the exposure value of the pattern for the portion tobe the protrusion can be suppressed to some extent.

(9) The distinctive feature is to use the mask forming the wider patternwidth than the design value for the purpose of preventing the patternwidth formed on the CF substrate from narrowing by suppressing thetransmissivity. The problem that the protrusion portion narrows due toinsufficient exposure value can be dealt by widening the width of theprotrusion pattern in the mask with a consideration of the narrowedamount for the part to be narrowed.

Next, a fabrication method of the liquid crystal display according to aseventh embodiment of the present invention is described with referenceto FIG. 21 through FIG. 25. This embodiment is according to the sixthaspect of the present invention.

While the example using the pillar-shaped spacer for obtaining thepredetermined cell gap is described in the above embodiments, aspherical bead made of plastic or glass is also used to realize the gap.Usually, these materials for the spacer are dispersed on either the TFTsubstrate or the CF substrate during a spacer dispersion process priorto laminating the substrates. Then, both substrates are laminated andfurther pressed so that the space between the substrates is maintainedat the thickness adjacent to a diameter of the spacer material.

However, in the MVA liquid crystal display, since the protrusions 20exist on the surface of both substrates 22 and 24 as shown in FIG. 21, asituation occurs in which a stable cell gap can not be obtained becausethe spacer 55 makes the wider cell gap thicker by going up on theprotrusion 20 or the cell gap is determined outside the protrusion 20.

Further, due to a shifting of the spacer 55 after laminating thesubstrates 22 and 24, the cell gap easily lacks uniformity in a planeand irregularities in display due to a change in cell gap are generated.Specifically, there is a problem that the display quality is degradedwhen the spacer 55 is shifted due to a vibration or an impact applied tothe liquid crystal display.

Furthermore, according to the MVA method, the protrusion 20 is requiredto be formed on the CF substrate 22 prior to coating the alignmentcontrol film. However, due to this formation of the protrusion 20, aphenomena that the alignment control film 28 repels on and around theprotrusion 20 as shown in FIG. 22 can occur. Therefore, the alignmentcontrol capability at the repelling portion 29 is remarkably reduced,thereby causing a display defect.

In this embodiment, the above problems are solved by the measuresdescribed below.

FIGS. 23 a and 23 b show a structure in a pixel of the liquid crystaldisplay, according to this embodiment. FIG. 23 a shows a cross sectionof this liquid crystal display and a state of the liquid crystal LC whenno voltage is applied. FIG. 23 b shows an alignment state of theelectric line of force and the liquid crystal molecules when a voltageis applied. The liquid crystal display according to this embodiment hasa distinctive feature that the TFT substrate 24 side is a normal TFTsubstrate for the MVA, as shown in FIGS. 23 a and 23 b, forming the slit20 for alignment control on the pixel electrode 16, but the slit foralignment control or the protrusion 20 is not formed on the CFsubstrate. Instead, an insulation layer 21 for alignment control isprovided.

The BM made of chrome film which decides each pixel is formed on the CFsubstrate 22 and the color filter is formed by one of the color resinsR, G and B corresponding to each pixel. A groove is formed in each colorfilter in parallel with the slit 20 for alignment control provided onthe TFT substrate 24. The common electrode 26 made of the ITO film isformed on the whole surface of the CF substrate 22 and the insulationlayer 21 for alignment control is formed on the ITO film in this groove.A vertical alignment film 28 is formed on the surface of the insulationlayer 21 for alignment control and on the surface of the color filter.The height of the insulation layer 21 for alignment control from thesurface of the substrate 1S formed to be substantially the same as orlower than the height of the color filter, where the surface of thesubstrate on the liquid crystal side of the CF substrate 22 is used as areference.

In this way, the CF substrate 22 with a flat substrate surface can beformed, thereby eliminating the repelling 29 on the alignment film 28,and preventing a reduction in alignment control capability. Further, asthe flatness on the surface of the CF substrate 22 improves, variationsof the cell gap due to the alignment control pattern can be preventedand a stable cell gap can be obtained.

FIG. 24 shows an example of a deformation of this embodiment. Thestructure shown in FIG. 24 has a distinctive feature that the BM and theinsulation layer 21 for alignment control are formed together by thesame material. By forming the insulation layer 21 for alignment controland the BM together by the same material after forming the color filterand the common electrode 26, the insulation layer 21 for alignmentcontrol can be formed without an increase in step of the fabricationprocess.

Further, as shown in FIG. 24, since an oblique electric field can besuppressed by forming the BM with the thick insulation film, theoccurrence of the alignment defect β (shown by a dashed-line ellipse)due to the oblique electric field occurring between the pixels in thepixel electrode 16 on the TFT substrate 24 side can be suppressed,thereby improving the quality of the display by suppressing thealignment defect at the end portion of the pixel.

Next, a specific fabrication method of the CF substrate 22 shown inFIGS. 23 a and 23 b is described. First, the BM 1S formed by forming ametal film (for example, Cr (chrome))on the glass substrate andpatterning. Next, by using a coating method such as a spin coatingmethod and the like, a photosensitive pigment dispersion type resin R(red) is evenly coated to approximately 1.5 μm in thickness. Next,pre-baking, exposure, developing and post-baking are performedsequentially, thereby forming a red color filter. During this patterningprocess, the groove to embed the insulation film 21 for the alignmentcontrol of the liquid crystal is also formed. By repeating this processfor G (green) and B (blue) in the same manner, three colored colorfilters are formed.

Next, the common electrode 26 is formed by depositing the ITO film toapproximately 100 nm in thickness by sputtering. Next, by using thecoating method such as the spin coating method, photo resist is evenlycoated on the surface of the substrate into substantially the same filmthickness as the color filter. Then, the insulation film 21 foralignment control is formed by sequentially performing pre-baking,exposure, developing and post-baking.

The difference in film thickness between the insulation film 21 foralignment control and each color filter is desired to be less than 0.3μm when the desired cell gap is 4 μm. Further, the use of photo resistwith a good flatness such as a polyimide type, a novolak type, an epoxytype, an acrylic type or the like is preferred as the photo resist whichis the forming material of the insulation film 21 for alignment control.

Furthermore, although Cr is used for the BM in the fabrication methoddescribed above, the pattern may certainly be formed by using othermaterials or methods such as a non-photosensitive resin, aphotosensitive resin or dying method and the like. Further, although thephotosensitive colored resin is also used to form the color filters, apattern may certainly be formed by using other materials or methods suchas a non-photosensitive resin, a photosensitive resin or dying methodand the like. Furthermore, although photoresist is used to form thepattern of the insulation film 21 for the liquid crystal alignmentcontrol, other material or method may certainly be used.

Next, a specific fabrication method of the CF substrate 22 shown in FIG.24 is described. First, by using a coating method such as the spincoating method and the like, photosensitive pigment dispersion typeresin B (blue) is evenly coated to approximately 1.5 μm in thickness onthe glass substrate. Then, the blue color filter is formed by performingpre-baking, exposure, developing and post-baking. During this patterningprocess, a groove to embed the insulation film 21 for the liquid crystalalignment control is also formed. By repeating this process for G(green) and R (red) in the same manner, three-color color filters areformed.

Next, the ITO film is deposited to approximately 100 nm in thickness onthe CF substrate 22 by sputtering, thereby forming the common electrode26. Next, by using a coating method such as the spin coating method,negative type photosensitive pigment dispersion type resin (black) isevenly coated on the surface of the substrate to substantially the samefilm thickness as the color filter. Then, the insulation film 21 foralignment control and the BM are formed by sequentially performingPre-baking, exposure, developing and post-baking.

Although photosensitive colored resin is also used to form the colorfilter in the fabrication method described above, a pattern maycertainly be formed by using other materials such as non-photosensitivecolored resin or other methods such as the dyeing method. Further,although negative type photosensitive pigment dispersion type resin isused to form a pattern for the alignment control insulation film 21 andthe BM, the pattern can also be formed by using other materials ormethods.

Hitherto, two photo masks are used and two photolithography processesare required in forming the BM for the CF substrate 22 and theinsulation film 21 for alignment control. However, the formation methodin the above example requires one mask and one photolithography process,thereby simplifying the process. Furthermore, when negative type photoresist is used as the material to form the insulation layer 21 foralignment control and the BM, a pattern without deviations inpositioning can be formed by performing a back exposure using thepattern for the color filter as the mask and by self aligning.

As described above, by the insulation layer 21 for alignment controlaccording to this embodiment, the cell gap can be stabilized,disclination can be suppressed, the alignment defect due to therepelling on the alignment film occurring on the protrusion foralignment control can be prevented, thereby improving the quality ofdisplay of the MVA liquid crystal display and simplifying thefabrication process.

The present invention is described in detail above. However, the presentinvention is not limited to the above-described embodiments anddeformations are possible to the extent not to deviate the presentinvention.

Further, in this embodiment, the following structures can also bedistinctive features.

1) The distinctive feature is that when the film thickness of the BM islarge, the insulation film for alignment control is not overlaid on theBM.

(2) The distinctive feature is that the film thickness of the BM is morethan 0.5 μm.

Next, a fabrication method of the liquid crystal display according to aneighth embodiment of the present invention is described with referenceto FIG. 26 through FIG. 31. This embodiment is according to the seventhaspect of the present invention.

This embodiment relates to a structure of a storage capacitor electrodeof the MVA liquid crystal display. Although the structure of the storagecapacitor electrode at each pixel is not mentioned at all sincedescription is not required for the above embodiments, an improvement ofthe storage capacitor electrode is described in this embodiment.

FIG. 26 shows a general structure of the storage capacitor electrodeformed on the TFT substrate of the MVA liquid crystal display. Further,FIG. 27 shows a cross section cut at a line A-A in FIG. 26. A gate busline 10 and a storage capacitor wiring 60 formed simultaneously with aformation of the gate bus line 10 are formed on the TFT substrate 24 inFIG. 26 and FIG. 27. A storage capacitor electrode 62 is formed on thestorage capacitor wiring 60 via a gate insulation film 64 and thestorage capacitor electrode 62 is connected with the pixel electrode 16via a contact hole 66 formed on a protection film 68. A storagecapacitor is formed by the storage capacitor wiring 60, the gateinsulation film 64 and the storage capacitor electrode 62. A slit 16 afor the alignment control of the liquid crystal is provided in the pixelelectrode 16.

However, when the storage capacitor electrode 62 is formed by such astructure, if the storage capacity is increased to improve voltageholding characteristics of the pixel electrode 16, the areas of thestorage capacitor electrode 62 or the storage capacitor wiring 60 mustbe increased, therefore resulting in a reduction in aperture ratio.Further, the area of the slit 16 a for alignment control of the liquidcrystal in the pixel electrode 16 becomes the area which should beshaded using the alignment of the liquid crystal. However, since shadingby the liquid crystal is not complete, there is some light leakage fromthe slit 16 a, thereby resulting in a reduction in contrast.

In this embodiment, in order to solve the above problems, a part of thestorage capacitor electrode is placed just under the slit (orprotrusion) 16 a for the alignment control of the liquid crystal. Inthis manner, storage capacity is also formed under the slit 16 a. Thestorage capacity can be increased without a reduction in aperture ratioin the storage capacitor electrode according to this embodiment.Further, in an etching to form the storage capacitor electrode and thegate electrode, since the area to be etched is reduced, the etching timecan be reduced.

Furthermore, shading of the protrusion (not shown) for alignmentcontrol, formed above the slit 16 a for the alignment control of theliquid crystal or the pixel electrode 16, becomes complete by thestorage capacitor electrode and contrast is also improved.

Description with reference to specific examples follows below.

FIG. 28 shows a structure of the storage capacitor electrode formed onthe TFT substrate of the MVA liquid crystal display of this example.Further, FIG. 29 shows a cross section cut at a line B-B in FIG. 28.Furthermore, a cross section cut at a line A-A in FIG. 28 is similar tothe one in the FIG. 27. The difference from the storage capacitor shownin FIG. 26 is that a storage capacitor wiring 60 electrically connectedto and branched off from the storage capacitor wiring 60 is formed justunder the slit 16 a. An additional storage capacitor is formed by thisstorage capacitor wiring 60′, the gate insulation film 64, theprotection film 68 and the pixel electrode 16.

FIG. 30 shows a deformation example of a variation of the structure ofthe storage capacitor electrode formed on the TFT substrate of the MVAliquid crystal display according to this example. Further, FIG. 31 showsa cross section cut at a line C-C in FIG. 30. The difference from thestorage capacitor shown in FIG. 28 is that a storage capacitor electrode62′ is wired between the gate insulation film 64 and the protection film68 which are located in the area between the storage capacitor wiring60′ formed just under the slit 16 a and the pixel electrode 16. Thestorage capacitor shown in FIG. 31 is formed by the storage capacitorwiring 60′, the gate insulation film 64, the storage capacitor electrode62′, the protection film 68 and the pixel electrode 16. In comparisonwith the structures in FIG. 28 and FIG. 29, larger storage capacity canbe obtained in the structures shown in FIG. 30 and FIG. 31.

When structuring as FIG. 30, as in an example, an increased capacity inthe area below the slit is equal to 1100 μm². Therefore, while thecapacity is approximately 936 μm² according to the structure shown inFIG. 26 even when the width of the storage capacitor wiring becomes from12 μm to 4 μm, the capacity according to the structure shown in FIG. 30becomes 2512 μm². Further, while the aperture ratio in the structureshown in FIG. 26 is 46%, the aperture ratio can be increased to 48% inthe structure in FIG. 30.

Furthermore, although the above example is described when the slit 16 ais formed in the pixel electrode 16, the similar effect can be achievedwhen the protrusion 20 for alignment control is formed on the pixelelectrode 16.

As described above, according to this embodiment, the storage capacitycan be increased without a reduction in aperture ratio. Further, sincethe etching area is reduced, the etching time when forming the storagecapacitor electrode 60 and the gate bus line 10 can be reduced.Furthermore, shading in the slit or the protrusion portion for thealignment control of the liquid crystal becomes complete by the storagecapacitor electrode, thereby also improving a contrast.

The present invention is described in detail above. However, the presentinvention is not limited to the above-described embodiments andvariations are possible to the extent which does not to deviate thepresent invention.

Further, in the present invention, the following structures can also bedistinctive features.

(1) The distinctive feature is that the storage capacitor wirings 60 and60′ are formed by the same material as and simultaneously with the gatebus line 10.

(2) The distinctive feature is that the storage capacitor wirings 60 and60′ are formed by the material having a shading capability.

As described in detail above, according to the present invention, aliquid crystal display becomes a preferable liquid crystal display whichis high in brightness and has a light display characteristic because itis possible not to generate an alignment defect area or not to show thedefect area in the display domain even if the defect area occurs.

Further, the liquid crystal display is to have a high fabrication marginand high yield as well as preferable display characteristics, since thedisplay is structured so that the alignment defect area occurs in theportion apart from the display domain even if the defect area occurs andthe display defect due to a small deviation during the fabrication doesnot occur.

1. A liquid crystal display comprising: a color filter formed on a CFsubstrate; a pixel electrode formed in each of a plurality of pixels ona TFT substrate; a liquid crystal having a negative dielectricanisotropy sealed between the CF substrate and the TFT substrate; astructure for controlling an alignment of the liquid crystal provided toat least the TFT substrate; a storage capacitor wiring arranged underthe structure on a side of the TFT substrate via an insulation film; anda storage capacitor formed by the storage capacitor wiring, theinsulation film and the pixel electrode.